Mac OS X Tiger/Utilities/Grapher

Grapher, an app that’s new in Tiger, is like your average high school graphing calculator on steroids. Not only can it create garden-variety 2D graphs, but also highly complex 3D ones, as well. Unlike most graphing calculators, the graphs that are created do not need to be functions. For example, one can enter as an equation $y^2=x^3-x$ and get the graph: